1. Field of the Invention
This invention relates to an automatic transmission for a motor vehicle that includes planetary gearsets and clutches and brakes whose state of engagement and disengagement determines speed ratios produced by the transmission.
2. Description of the Prior Art
In a front wheel drive vehicle, the axial space available for the transmission is limited by the width of the engine compartment and the length of the engine. In addition, the trend to increase the number of ratios available generally increases the number of components required. For these reasons, it is desirable to position components concentrically in order to minimize axial length. The ability to position components concentrically is limited, however, by the need to connect particular components mutually and to the transmission case.
Furthermore, it is desirable for the output element to be located near the center of the vehicle, which corresponds to the input end of the gear box. An output element located toward the outside of the vehicle may require additional support structure and add length on the transfer axis. With some kinematic arrangements, however, the need to connect certain elements to the transmission case requires that the output element be so located.
An automatic transmission conventionally includes a manual valve, which is moved by a cable in response to manual movement of the gear selector to the selected range position. Shift-by-wire and range-by-wire selector systems usually have no manual valve, thereby requiring some other means to protect against energizing a solenoid or engaging a gear that is other than the solenoid or gear corresponding to the selected range.
Generally the lube flow rate is set at a rate required to maximize the service life of the clutches, brakes, gears and bearings due to a maximum torque condition. This flow rate is usually greater than that required for normal driving conditions.
A need exists for a device that provides both a lube path, in which lubricant flows to cool and lubricate the clutches, brakes, gears and bearings of the transmission and a parallel path to the sump.